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Performing vital pulpotomies: why and how (Proceedings)

Dentinal pulp occupies the interior cavity of the tooth. It consists of loose connective tissue intercellular substance, vessels, nerves, and fibers. Anatomically, the pulp is divided into a coronal pulp and root pulp, corresponding to the anatomical crown and the root. The anatomical crown is covered by enamel. In older animals, there may be differences in the distribution and density of cells and fibers of the root canal, however there is no principal difference in the tissue constituents. The outline of the pulp chamber, particularly in young animals teeth, usually follows the exterior morphology of the dentin. As the animal ages the pulp chamber is reduced by continual dentinal deposition throughout, and markedly reduced in areas of attrition.

Histology

The pulp morphologically is divided into four areas: 1) the odontoblastic layer covering the periphery of the pulp chamber, enclosed in dentine, with processes extending into the dentinal tubules. 2) the layer of Weil (cell poor layer), that appears next to the odontoblastic layer in mature teeth 3) a cell rich layer, between the cell poor layer and the central pulp and 4) the pulpal center. The pulal center differs from the rest of the pulp only by having a smaller number of cells per unit than the cell rich layer.

The pulp connects with the periapical tissue through apex in each root, with the possibility of many shapes and apical foramina in each tooth. The vetodontist must be aware of this phenomenon. It is of the utmost importance in endodontic therapy. In young animals in which the apical foramen is not yet fully developed, the pulp connects with the surrounding periapical tissue in a wide area. During development of the root, the foramen narrows by lengthening of the root and by deposition of dentin and cementum, but during this period the walls of the foramen still consist entirely of dentin. With increasing age and with exposure to physiologic functioning, a layer of cementum may cover the dentin at varying lengths into the root canal. Cementum does not maintain an equal distance from the foramen throughout the circumference of the root canal. Root development usually results in one main and one or more lateral canals, in ground sections, appearing as an apical delta of varying configurations.

Lateral or accessory canals, though not as common in dog and cats, may occur and connect the pulpal tissue with the periodontal ligament at any level of the root, but are most frequently found in the apical third of the root. Connective tissue of the pulp continues directly to the periodontal ligament through these lateral and accessory canals. Endodontic success may be influenced by the obturation of these canals especially those of significant diameter. In cases of progressing periodontal disease, if the bacterial plaque reaches and involves the soft tissue of lateral canals, pulp involvement will result.

Pulpal function

Pulpal functions are formative, nutritive, sensory, and defensive - formative in that it produces dentin. The development of the pulp is a gradual process that varies with the individual tooth. Development of the pulp takes place after the development of the dental organ, from mesenchymal cells, known as the dental papilla, directly under the dental organ. A distinct basement membrane divides the cellular elements of the dental organ and the dental papilla from each other, and the concentration of cells in the dental papilla stands out clearly from the surrounding oral tissues.

Dentin and pulp share an integral relationship with the odontoblastic processes. When a lesion invades the dentin, the odontoblastic processes and the pulp are involved.

As maturation occurs additional layers of dentin are added. Each dental tubule containing a vital odontoblast. The dentinal tubule tapers to a cone like shape to the dentinoenamel/dentinocementum junction. The dentinal tubules and odontoblastic process are less voluminous at the periphery of the tooth tapering to a almost closed structure at the cemental wall. The cellular, cytoplasmic content of the dentinal tubules is significant in all endodontic treatment. Open dentinal tubules can lead to pulpal pathology.

Normal healthy pulpal tissues continue dentinal deposition at a slow rate throughout life. This is referred to as "calcifying down" of the pulp chamber. Pulpal pathology decreases dentinal deposition. Dentin deposition ceases with tooth mortality